Increasing aggregate concentration in the economy has increased attention to the issues surrounding the outside ownership of enterprises. Outside ownership entails both industrial diversification and various forms of conglomerate ownership and represents an important new direction for studies of economic sociology and labor market segmentation. The article shows that the influence of four measures of outside ownership on worker's earnings and tenure is largely, though not universally, negative. Outside ownership tends to suppress earnings otherwise accruing to workers in companies with high levels of unionization, rapid growth, and high profits. Workers' tenure is influenced negatively by some types of outside ownership but positively by others. Tenure is reduced in subsidiary firms and in industries predominately owned by other industries due to reduced union influence on job tenure in these settings. Average tenure is increased in companies that are spread across several industries. These findings provide little support for dual labor market theories and other economic theories that argue that workers benefit from the market power of their employing organizations. Instead, the findings provide support for theories that stress the dangers to workers' fates arising from the increasing dominance of financial management in economic decision making.